Improvement in photolithographic transfers



' NITED STATES PATENT OFFIGE.

JNO. W; OSBORNE, OF MELBOURNE, AUSTRALIA, ASSIGNOR TO SAML. T. HOOPER, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN PHOTOLITHOGRAPHIC TRANSFERS.

Specification forming part of Letters Patent No. 33,172, dated August 27, 1861.

To all whom it may concern:

Be it known thatI, JOHN WALTER OSBORNE, of the city of Melbourne, in the county of Bourke, in the Colony of Victoria, in the dominions of Her BritannicMajesty, have invented a new and Improved Mode of Preparing Photolithographic Transfers; and I do hereby declare that the following is a full and exact description thereof.

The nature of my invention consists in applying retransfer-ink to the dry surface of the photographic print.

To enable others skilled in the art of photolithography to make use of my invention, I a

will proceed to describe how the process may be performed.

A sheet of photolithographic transfer-paper having been prepared with the positive photographic print of the design which it is proposed to transfer to the surface of a lithographic stone, or zinc plate, or other surface suitable for printing from, this photographic positive print is next to be inked in by passing it in its dry state through the lithographic press with its face toward a lithographic stone or plate, said stone or plate having been first evenlyrolledinwith lithographic retransfer-ink or an equivalent greasy or resinous substance. When the paper is pulled off the stone the greasy ink should be found to be of such a thickness as to disclose the positive print dimly through it. 'In Poitevins process the method of inking differs from mine. He inks the exposed surface in a moistened state. I, on the contrary, ink it while dry. v and wets his transfer and applies the ink while it is wet.

From the foregoing references it will be seen that I do not claim to be the original inventor of photolithography.

What I claim as my invention, and desire to secure by Letters Patent, is

The method hereinbefore described of inkin g with a greasy ink the whole surface of the sensitive transfer-paper, after exposure of the same to light under a negative, before Wetting or moistening it, and subsequently removing the superfluous portions of the ink in the manner detailed in Letters Patent of the United States issued to Samuel Thompson Hooper, assignee of John Walter Osborne, on the 25th day of June, 1861, for improvements in photolithography.

J. W. OSBORNE.

In presence of-- W. F. ROWE, O. V. Ross.

Asser also washes I 

